Losses of electronic components attributable to electrostatic discharge amounts to tens of millions of dollars each year. Typically a tray or tote bin of electronic components such as integrated circuit chips, in being moved around, picks up a charge of thousands of volts which can reach 30,000 volts when the air is dry. These charges are generated by two surface rubbing or sliding in contact with each other.
When a so charged component is touched or put down, the charge is suddenly discharged, destroying or damaging the component. For this reason, electronic components are packageo in conductive containers. Workers wear special conductive clothing and shoes. Employees are grounded via wrist bands and floor mats. Air is conditioned and ionized. An important factor in controlling static electric discharge (ESD) in clean rooms is the conductivity of the floor covering. A desirable range for resistance to ground is above 2.5.times.10.sup.4 ohms up to a maximum of about 10.sup.6 ohms or at most 10.sup.7 ohms volume resistance. For this reason, a metal floor is not su:table as it is too conductive.
In order to reduce resistance of typical flooring materials, several different systems have been proposed These include coating a floor with a conductive floor wax, and inclusion of conductive particles in the floor surface However, conductive wax scuffs, collects dirt, flakes off and needs to be replaced per:odically. Conductive vinyl or laminate typically contains carbon particles in the surface; in normal usage, the laminate surface wears and consequently carbon particles wear off or dust from the surface and the resultant carbon dust is dispersed :nto the atmosphere. This conductive dust is not desirable as it may cause short circuits when particles fall onto and into electrical components.
Considerable interest has been expressed in recent years for static dissipative and electrically conductive laminates for use in various env:ronments, including static dissipative work surfaces and conductive flooring. Among the recent patents there may be mentioned the U.S. Pat. No. 3,922,383 to Wilks et al; U.S. Pat. No. 4,472,474 to Grosheim et al; U.S. Pat. Nos. 4,480,001 and 4,540,624 to Cannady et al; U.S. Pat. Nos. 4,454,199 and 4,455,350 to Berbeco. The use of carbon filled laminate paper is known, as is the use of salts, the latter having been previously known noting patents such as Meiser U.S. Pat. No. 3,650,821 and Economy et al U.S. Pat. No. 3,567,689. No one product is suitable for all static dissipative and conductive environments, because different usages, i.e. environments, require different properties.
The Department of Defense defines the following relationship between static electrical properties and surface resistivity (in ohms/square):
Anti-static: greater than 10.sup.9 ; PA0 Static dissipative: between 10.sup.6 and 10.sup.9 ; PA0 Conductive: less than 10.sup.6. Surface resistivity of standard high pressure decorative laminate is about 10.sup.11 to 10.sup.13 ohms per square.